Uranium(IV) Imidazolin-2-iminato Complexes: A New Class of Actinide Complexes

Acid–base reactions between imidazolin-2-imines (ImRNH) and [U­(NMeEt)4] selectively afforded uranium­(IV) imidazolin-2-iminato complexes of the type [U­(NImtBu)4] (1), [U­(NImMes)3(NMeEt)] (2), and [U­(NImDipp)2(NMeEt)2] (3) depending on the steric demand of the substituents in the 1 and 3 positions of the imidazole heterocycle (R = tBu, Mes, Dipp). This new class of actinide complexes displays short U–N bonds and nearly linear U–N–C bond angles, suggesting a U–N bond order higher than 1, as well as extraordinarily high catalytic activity in the polymerization of ε-caprolactone.